1. Field of the Invention
This invention relates to an apparatus for manufacturing microarray chip for use in DNA analysis, immunological analysis, and the like, and more particularly to an improvement in the structure for spotting specific binding substances onto a chip.
2. Description of the Related Art
Recently, genetic engineering has exhibited rapid progress, and the human genome project for decoding the base sequence of human genomes which amount to 100,000 in number is progressing. Further, enzyme immunoassay, fluorescent antibody technique and the like utilizing antigen-antibody reactions have been used in diagnoses and studies, and studies for searching DNAs which affect genetic diseases are now progressing. In such a situation, a microarray technique is now attracting attention.
In the microarray technique, a microarray chip (sometimes called DNA chip) comprising a plurality of known cDNAs (an example of specific binding substances) spotted in a matrix on a chip such as of a membrane filter or a slide glass at a high density (at intervals of not larger than several hundred xcexcm) as shown in FIG. 5 is used and DNAs (an example of organism-originating substances) taken from cells of a normal person A and labeled with a fluorescent dye a and DNAS taken from cells of a genetic-diseased person B and labeled with a fluorescent dye b are dropped onto the microarray chip by pipettes or the like, thereby hybridizing the DNAS of the specimens with the cDNAs on the microarray chip. Thereafter, exciting light beams which respectively excite the fluorescent dyes a and b are projected onto the cDNAS by causing the exciting light beams to scan the microarray chip and fluorescence emitted from each of the cDNAS is detected by a photodetector. Then the cDNAs with which the DNAs of each specimen are hybritized are determined on the basis of the result of the detection, and the cDNAs with which the DNAs of the normal person A are hybridized and those with which the DNAs of the diseased person B are hybridized are compared, whereby DNAs expressed or lost by the genetic disease can be determined. This information contributes to gene therapy.
The number of specific binding substances such as cDNAs have been spotted on a chip such as of a membrane filter or a slide glass at a high density by means of a microarray chip manufacturing apparatus(a spotter or an arrayer) as shown in FIG. 3.
In the microarray chip manufacturing apparatus shown in FIG. 3, there is used a microtiter plate 10 having a number of specific binding substance holes 10a which are two-dimensionally arranged at pitches P larger than pitches at which the specific binding substances 11 are to be spotted onto a chip 20. The specific binding substance holes 10a are respectively filled with the specific binding substances 11. The microarray chip manufacturing apparatus comprises a spot head 30 provided with a plurality of, e.g., twoxc3x97two, specific binding substance picking pins 31 which are arranged at the same pitches as the pitches P at which the specific binding substance holes 10a of the microtiter plate 10 are arranged, and a means for moving the spot head 30.
The microtiter plate 30 is about 8 cmxc3x9712 cm in size and the number of the specific binding substance holes 10a on the microtiter plate 30 is generally in the range of 8xc3x9712 (=96) to 32xc3x9748 (=1536). To the contrast, the chip 20 on which the specific binding substances 11 are spotted is about 2 cmxc3x972 cm in size operation of a microarray chip manufacturing apparatus which spots 96 specific binding substances 11 onto a chip 20 by the use of a microtiter plate 10 having 8xc3x9712 specific binding substance holes 10a will be described, hereinbelow.
First the spot head 30 is moved to a position where the four picking pins 31 are aligned with the upper left four (2xc3x972) specific binding substance holes 10a and then moved downward so that the picking pins 31 are inserted into the respective specific binding substance holes 10a and the specific binding substances 11 therein adheres to the picking pins 31. Thereafter, the spot head 30 is moved upward and to the chip 20 and then moved downward so that the picking pins 31 are brought into contact with the chip 20, whereby the specific binding substances 11 on the respective picking pins 31 are spotted onto the chip 20 as shown in FIG. 4A. In FIG. 4A and the following FIGS. 4B to 4D, the small circles indicated at xc3x97 show the specific binding substance holes 10a into which the picking pins 31 are inserted at that time. When a plurality of microarray chips are to be manufactured, the same procedure is repeated the like number of times.
Then the specific binding substances 10a in the four holes 10a on the right side of the holes 10a the specific binding substances 11 in which are initially spotted (i.e., third and fourth holes 10a in the uppermost line as numbered from the left and third and fourth holes 10a in the second uppermost line as numbered from the left) are picked. At this time, since the specific binding substances 11 in the respective holes 10a are generally different from each other, it is necessary to clean the pins 31 by ultrasonic cleaning and to dry the same prior to picking the next specific binding substances 11 in order to prevent the preceding specific binding substances 11 from mingling with the next specific binding substances 11. After cleaning and drying the pins 31, the pins 31 are inserted into the next four holes 31 and the spot head 30 are moved so that the specific binding substances 11 in the holes 31 are spotted onto the chip 20 on the right side of the preceding spots at distances therefrom smaller than the distance (pitch) P between the pins 31 (e.g., P/6) as shown in FIG. 4B.
After these procedure (including picking, spotting, cleaning and drying) is repeated six times and the specific binding substances 11 in the upper right four holes 10a (i.e., first and second holes 10a in the uppermost line as numbered from the right and first and second holes 10a in the second uppermost line as numbered from the right) are spotted onto the chip 20, twenty-four specific binding substances 11 are spotted onto the chip 20 in two lines as shown in FIG. 4C.
Thereafter, the specific binding substances 11 in the holes 10a on the third and fourth lines are spotted onto the chip 20 on the lower side of the preceding spots at distances therefrom smaller than the distance (pitch) P between the pins 31 (e.g., P/4) as shown in FIG. 4c. 
The procedure described above is repeated until the specific binding substances 11 in all the ninety-six holes 10a are spotted onto the chip 20 as shown in FIG. 4D.
In the conventional microarray chip manufacturing apparatus, the picking pins must be cleaned and dried each time they spot four specific binding substances. This means that cleaning and drying must be repeated twenty-four times four a chip 20 bearing thereon ninety-six (96) specific binding substances 11 (96/4=24) and three hundred and eighty-four (384) times for a chip 20 bearing thereon one thousand five hundred and thirty-six (1536) specific binding substances 11 (1536/4=384). The operation of cleaning and drying the picking pins requires a long time and deteriorates the efficiency of the spotting.
Further, the preceding specific binding substances 11 adhering to the picking pins cannot be perfectly cleaned, which gives rise to a problem that there is fear that the next specific binding substances 11 can be contaminated by the preceding specific binding substances.
In view of the foregoing observations and description, the primary object of the present invention is to provide a microarray chip manufacturing apparatus which can spot specific binding substances onto a chip in a shorter time.
The microarray chip manufacturing apparatus in accordance with the present invention is characterized in that the spaces among the picking means (e.g., picking pins, picking nozzles or the like) are changed when the picking means spot specific binding substances from those when the picking means pick the specific binding substances.
That is, in accordance with the present invention, there is provided a microarray chip manufacturing apparatus comprising a plurality of picking means which pick specific binding substances linearly or two-dimensionally arranged at first spaces and spot the specific binding substances onto a flat chip at second spaces narrower than the first spaces, wherein the improvement comprises
that the picking means are movable so that the spaces among the picking means can be switched between said first spaces and said second spaces, and a space switching means switches the spaces among the picking means to said first spaces when the picking means pick the specific binding substances and to said second spaces when the picking means spot the specific binding substances onto the chip.
The specific binding substances may be, for instance, organism-originating substances such as cDNAs, and may be held in holes formed on a microtiter plate arranged linearly or two-dimensionally.
When the specific binding substances are held on a microtiter plate, the first spaces may be, for instance, about 1 mm to 10 mm and the second spaces may be, for instance, about 100 xcexcm to 500 xcexcm.
The flat chip is a substrate such as of a membrane filter or a slide glass which is spotted with the specific binding substances to form a microarray chip.
The space switching means may be of any structure so long as it can switch the spaces among the picking means between said first spaces and said second spaces. For example, the space switching means may comprise bellows connecting the picking means and a means for linearly or two-dimensionally expanding and contracting the bellows.
It is preferred that the picking means be provided in the same number as the number of the specific binding substances so that all the specific binding substances can be spotted onto the chip in one action.
In the microarray chip manufacturing apparatus of the resent invention, by switching the spaces among the picking means to the first spaces, equal to the spaces at which the specific binding substances are arranged, when the picking means pick the specific binding substances and to the second spaces, at which the specific binding substances are to be spotted onto the chip, when the picking means spot the specific binding substances onto the chip, a larger number of specific binding substances can be spotted at one time, whereby the time required to spot the specific binding substances can be shortened and at the same time, contamination of the specific binding substances with those spotted previously due to repeated use of the same picking means can be suppressed.
Further, when the picking means are provided in the same number as the number of the specific binding substances, all the specific binding substances can be spotted onto the chip at one time, whereby the time required to spot the specific binding substances can be further shortened and at the same time, contamination of the specific binding substances with those spotted previously, which can occur when the same picking means are repeatedly used, can be prevented.